checkFencingConfigured

BadFencingConfigurationException - if the fencing configuration
appears to be invalid. This is divorced from the above
getFencer() method so that the configuration can be checked
during the pre-flight phase of failover.

getFencingParameters

addFencingParameters

Hook to allow subclasses to add any parameters they would like to
expose to fencing implementations/scripts. Fencing methods are free
to use this map as they see fit -- notably, the shell script
implementation takes each entry, prepends 'target_', substitutes
'_' for '.', and adds it to the environment of the script.
Subclass implementations should be sure to delegate to the superclass
implementation as well as adding their own keys.